Odd drilling troubles. Help?

D

deker

Joined
Nov 14, 2005
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3,496
So I have a knife I've been working on made from a piece of old lawnmower blade. Long before I forged out the blade the steel was heated to non-magnetic and left overnight in a bucket of vermiculite to anneal. Months later the blade was forged out to shape and I did a bit of grinding on it. Today I figured I'd get the holes drilled in the tang for the scales. First one was just fine. Second one, I got about 1/2-2/3 through and the bit stopped cutting. Seemed odd, so I swapped in a new bit. Still no dice. Pushed a little harder and snapped the new bit (1/8"). Took a torch to it and drew it to a dark blue. Tried again. Won't cut. Checked the bit on another piece of mild steel. Cuts just fine.

Ideas? Anybody?

Thanks,

-d
 
it needs to be anealed heat it up to nonmagnetic and let air cool
when it was a mower blade it might of been work hardened more in that area
 
How fast is the spindle speed on the drill press?? You might be trying to drill it too fast...
 
bartblade said:
it needs to be anealed heat it up to nonmagnetic and let air cool
when it was a mower blade it might of been work hardened more in that area
Click to expand...

Wouldn't that normalize it not anneal? Either way I suppose it'll soften it. It just seems odd that it's acting like this even though it's been annealed and forged.

I suppose it'll have to wait until the next time the forge gets fired up. On the good side, I bet it'll get really hard when I HT it :D

Thanks,

-d
 
Probably air hardened after the last heat when you were forging it. I've had a lot of trouble with O1 doing that, suppose other steels will do it just as easily. I'd heat it again and stick it back in the vermiculite before you try to drill anymore holes.
 
on the 2nd hole did you stop might have hardned the steel under the bit
since we dont know what kind of steel it is it might be some kind of air hardening type
just a thought
butch
 
Another trick I learned in drilling spring/tool steel (not hardened) is to spread the stress on the bits by doing two or even three graduated sizes up to the desired size. I also use a constant spray of WD-40 or the likes and continuous non-stop pressure. This process allows you to use regular HSS bits and you end up with a neater hole in the end.

I won't mention how many bits I have smoked learning how to drill the stuff.:rolleyes:
 
tnmike:

I followed the guidelines on the speed selection chart on the press. It was a 1/8" bit, so I ran it at 3100RPM. Every other 1/8" hole I've drilled has cut like butter.

matt:

Suppose it's possible, just odd that it would only be in this one spot.

butch:

I did stop halfway to re-lube the bit. Did the same on the first hole.

BFinnigan:

I'd be afraid to see what would have happened if I had started at 1/16"!

I've got more pieces of tha same steel. Next time I fire up the forge I'll muck around with one and see if I can get a hint or two of what it is based on how it acts when quenched, what grain structure looks like, etc.

Thanks,

-d
 
3100rpm?!! way to fast. When drilling metal the slower the better. I run mine at 120rpm when drilling metal and If my press went slower I would use that speed. To much heat and friction builds up and instead of drilling you end up polishing the crap out of the hole and dulling your bit and then you can't get the bit to bite into the metal. Also what bits do you use? I have cobalt steel bits they seem to work the best for me.
 
i ll 2nd the speed way too fast go as slow as you can and use some good cutting lube that should fix the problem
least most of it i think you might have a hard spot now from the last bit that didnt make it
butch
 
I hate this problem. I have a chronic problem with a particular bar of 1095. It should be fully factory annealed, but often bits can get about 1/2 way from each side, and squeeeeel to a stop in the middle...almost like its case annealed, heh.....never figured out how to fix it beyond brute force and patience.
 
A little heat can be expected in any machining operation. The key is to be sure your speed and feed matches the diameter of your drill bit. Smaller bits, lets say, 1/8" and below require a higher speed, and a lighter feed. Larger bits require a slower speed, and a firmer feed for them to cut properly. The warning signs here are smoke and fumes. If you got them, then something is off.

When drilling, you should have two lovely curls of material coming from each side of the bit. This is how you know you are perpendicular to the material, and that your bits are sharp. I'm not even going to get off on a tirade about why you should keep your bits sharp.

I got to say that the best thing you can do to improve your drilling is to buy some good bits. Cobalts are cheap these days, and the imports seem to be coming through with some fair quality. I've been having some success experimenting with polished-flute bits from china, I ordered through MSC. They are fair for the price. Cheap enough to use a few times and toss when they get dull. I have been chopping the flutes off with a dremel wheel and saving the shanks to use as dowel pins.

Last but certainly not least would be coolant. Notice I said COOLANT - not lubricant. Why not lube? Lubricant... lubricates. Its that simple. Put lubricant on something and it slips. If you drill bit slips and does not do what it is designed to do, then its not performing its job, which is to bite into the material and shave an amount off, then it is making heat. Use lubricant for tapping, and use coolant for drilling in tool steels.

Grab any old household squeeze bottle and use it to lightly flood the drill bit with coolant. You wont need a tremendous amount, but surely enough to keep the bit and the material cool.

As far as coolants go, I like the synthetic kinds that can be diluted with water. Kool-Mist #77 is a good choice because you can also use it in a mister setup. I also use Syn-Kool by Rustlick. I actually use the Syn-Kool in my horizontal saw too.

Sorry for the long response, but I hope it will help. :thumbup: :)
 
jhiggins said:
A little heat can be expected in any machining operation. The key is to be sure your speed and feed matches the diameter of your drill bit. Smaller bits, lets say, 1/8" and below require a higher speed, and a lighter feed. Larger bits require a slower speed, and a firmer feed for them to cut properly. The warning signs here are smoke and fumes. If you got them, then something is off.

When drilling, you should have two lovely curls of material coming from each side of the bit. This is how you know you are perpendicular to the material, and that your bits are sharp. I'm not even going to get off on a tirade about why you should keep your bits sharp.

Last but certainly not least would be coolant. Notice I said COOLANT - not lubricant. Why not lube? Lubricant... lubricates. Its that simple. Put lubricant on something and it slips. If you drill bit slips and does not do what it is designed to do, then its not performing its job, which is to bite into the material and shave an amount off, then it is making heat. Use lubricant for tapping, and use coolant for drilling in tool steels.


:thumbup: :)
Click to expand...
well and i thought i was helping out :o
thanks for the good info no more lube for me then sept for tapping
i was just using the coolent for working with Ti cant wait to see how much better things work when i am doing it right
 
Unless I missed the suggestion in an eaarlier post, you might invest in a solid carbide bit. in 1/8", it won't cost a ton of money, and since they can break, a spare or so wouldn't hurt...
 
Cobalt should be used, slow, with NO lube.
HSS... Crisco is the best lube.
Ever drilled a Mauser receiver ?
I have..Hundreds.
Take it slow...
 
So, for tool steel, how many SFPM should I be running at? I'm with you on the smaller bits requiring higher speed Mr. Higgins, but I can't seem to find my copy of machinery's handbook. I do know that I get nice curls on mild steel with this bit at this speed.

I know cobalt bits, etc will work, but I see no reason that my TiN coated HSS bit shouldn't work on annealed stock. I'd much rather understand the problem and learn to overcome it properly than resort to brute force to fix it.

I should be able to anneal it this weekend if nothing else.

-d
 
"Tool Steels" covers a wide range but drilling SFPM would run in the 20-85 range. I've no idea what your lawnmower blade is made of, but I'd guess a medium carbon steel. You'd be safe at 50 sfpm. For an 1/8" HSS drill bit, that would translate to roughly 1528 RPM. The formula is RPM = 3.82 X SFPM/Diameter of Drill Bit. Use a coolant/lubricant for sure. Even WD-40 or Crisco can work in a pinch. Small drill bits need to spin at the correct speed, don't run them at a crawling speed. Way too slow and way too fast are both bad, but RPM recommendations have some leeway on either side.

Most steel is recycled these days and a lawn mower blade could have bits of harder alloys in it. I see this more and more even in premium steels. If you've already annealed the blade, then either its work hardened from the drill or in your case, probably hit something hard in the steel. The answer is to grind through the hard spot with a small grinding bit in a die grinder or dremel type tool.

Hope this helps,


George
 
gspam1 The formula is RPM = 3.82 X SFPM/Diameter of Drill Bit. George[/QUOTE said:
Beat me to it, George. Thanks! :thumbup:

One thing I might add here is that this is only a rough general speed you should be operating with that size bit. The rest is up to you, since your right arm is applying the downward force required to advance the bit through the material. Good luck, and go bore some holes!
Click to expand...
 
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